全新java初学者实践教程6(Java SE5.0版)
S82NU2L 基本语法3
O .TFV. JV36@DVQ 7Kk rfJqN 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
cuq7eMG6z Y@9L8XNP> [font="Times] 1.循环语句[font="Times]:while,do-while,for
tPO.^ ?9H7Twi+T [font="Times]2.分支语句[font="Times]:if-else,switch,
**_VNDK+ [font="Times]
|GdA0y\v*} 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
+A~lPXAXW [font="Times]
#xW%RF 4.异常处理语句[font="Times]:try-catch-finally,throw
3 [SN[faS ~-']Q0Z 实践:
iV'-j,-i [font="Times] 1.循环语句
v0"|J3 [font="Times] while 语句
I;P?P5H [font="Times]class While {
z9w@-]) [font="Times]public static void main(String args[]) {
yC+N18y? [font="Times]int n = 10;
K ANE"M [font="Times]while(n > 0) {
"'t<R}t!A [font="Times]System.out.println("tick " + n);
p\+#`] Q7} [font="Times]n--;
/D1Bf:'( [font="Times]}
gW/H#T, [font="Times]}
,=$yvZs4[] [font="Times]}
_\@i&3hkx [font="Times] do…while 语句
d2.n^Q"?3 [font="Times] class DoWhile {
"{z9 L+ [font="Times]public static void main(String args[]) {
`3pe\s [font="Times]int n = 10;
j@GMZz< [font="Times]do {
m9#u.Q* [font="Times]System.out.println("tick " + n);
U|{WtuR [font="Times]n--;
v bDw2 [font="Times]} while(n > 0);
o<Y|N [font="Times]}
+bdkqdB9 [font="Times]}
)Bb :tz+ 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
VZAdc*X [font="Times] for语句
OUI}jJw+ [font="Times] class ForTick {
ry~3YYEMI0 [font="Times]public static void main(String args[]) {
M#<x2ojW [font="Times]int n;
Z"Et]xSU%$ [font="Times]for(n=10; n>0; n--)
Sw5H+! [font="Times]System.out.println("tick " + n);
lz{>c.Ll[ [font="Times]}
1 _5[5K^ [font="Times]}
C>T6{$xkC 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
<>j,Q 还有啊,[font="Times]for循环的部分可以为空的
2i,Jnv=sR [font="Times]class ForVar {
'kH#QO\(e" [font="Times]public static void main(String args[]) {
{H])Fob [font="Times]int i;
`d
OjCA_& [font="Times]boolean done = false;
pM(y?zGt [font="Times]i = 0;
:\4O9f*5+ [font="Times]for( ; !done; ) {
})mez[UmZ [font="Times]System.out.println("i is " + i);
U}gYZi;;$ [font="Times]if(i == 10) done = true;
JiI(?I [font="Times]i++;
?MpGzCPa [font="Times]}
Q=^}B}G [font="Times]}
ya:H{#%6 [font="Times]}
循环语句的例子下载 l'
"< [font="Times] 2.分支语句[font="Times]
Nz!AR$
[font="Times] if/else语句
f{3FoN=z [font="Times]class IfElse {
TUpEhQ+* [font="Times]public static void main(String args[]) {
D"^ogY#LK [font="Times]int month = 4; // April
@Cz1rKU^l [font="Times]String season;
n8:2Z> [font="Times]if(month == 12 || month == 1 || month == 2)
*,'"\n [font="Times]season = "Winter";
t8?+yG; [font="Times]else if(month == 3 || month == 4 || month == 5)
[]dRDe;# [font="Times]season = "Spring";
QtN 0|q{af [font="Times]else if(month == 6 || month == 7 || month == 8)
3>L1}zyM] [font="Times]season = "Summer";
L {B#x@9tQ [font="Times]else if(month == 9 || month == 10 || month == 11)
L"}@>&6 [font="Times]season = "Autumn";
lPFMNRt~8 [font="Times]else
_I$]L8hC [font="Times]season = "Bogus Month";
<7PtC,74 [font="Times]System.out.println("April is in the " + season + ".");
A)`M*(~ [font="Times]}
l@j!j]nE [font="Times]}
k?J}-+Bm[| [font="Times]//这段程序输出[font="Times]:
D(h|r^5 [font="Times]//April is in the Spring.
2B!nLLCp+ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
>`oO(d}n[0 [font="Times] switch语句
w~Y#[GW [font="Times] class Switch {
^'[ | [font="Times]public static void main(String args[]) {
Q7}wY [font="Times]int month = 4;
VJ=!0v [font="Times]String season;
I gFz[)
[font="Times]switch (month) {
9R ugkGy [font="Times]case 12:
Z>M*!mQi [font="Times]case 1:
q5HHMHB [font="Times]case 2:
koqH~>ZtD [font="Times]season = "Winter";
E&[ox[g{ [font="Times]break;
7s.sbP~ [font="Times]case 3:
7,+:QY@ [font="Times]case 4:
VFYJXR{ [font="Times]case 5:
GbL,k?ey [font="Times]season = "Spring";
8=2)I. [font="Times]break;
jXW71$B [font="Times]case 6:
SR 43#!99Q [font="Times]case 7:
mS%D"
e [font="Times]case 8:
")sq?1?X [font="Times]season = "Summer";
DD~8:\QD [font="Times]break;
el[6E0!@ [font="Times]case 9:
w\@Anwj#L [font="Times]case 10:
^3r2Q?d\ [font="Times]case 11:
z ,ledTl [font="Times]season = "Autumn";
a(J~:wgd [font="Times]break;
oa9T3gQ? [font="Times]default:
\7/xb{z| [font="Times]season = "Bogus Month";
DAvAozM [font="Times]}
9k*'5(D4S [font="Times]System.out.println("April is in the " + season + ".");
PMTyiwlm [font="Times]}
|UlScUI, [font="Times]}
分支语句代码下载 wEkW= 3b[_0 [font="Times]switch语句适合于条件非常多的逻辑
BRW
请看上述语句可以混合使用,请看
下载例子